Diane Keaton calls as she's driving across the California desert. She will have to call back, oh, three or four times over the next half hour. The connection keeps breaking up, slipping into static, disappearing into the ether. Finally she just pulls over, somewhere over the Arizona border, and gets out of the car.

"It is 104 degrees," she says. "Well, OK." Pause. "Yeah." And laughs, for no particular reason. The giggle is like a little burst of "Annie Hall," as full of `70s bubbles as a Perrier.

Not that Keaton is trapped in that decade, or that role. Since that breakthrough, Oscar-winning performance Keaton has filled the years with new experiences and new challenges — directing features, putting out artbooks, writing memoirs (her latest is "Let's Just Say It Wasn't Pretty") and adopting two children.

"When you're young you can't know what being older is," says Keaton, 68. "Every decade of our lives, it's like we're entering a new arena, and we're completely unprepared. Here it comes, you know, and — oh, here I am. It's exciting."

Her latest film, "And So It Goes" (opening July 25) is mostly about that. In it, she's a sixtyish widow; Michael Douglas is a sixtyish widower. She's bohemian and very welcoming, he's stuffy and pretty insulting. But they find a few surprising things in common, and slowly connect. "It's about second chances," she says. "It's sweet."

One of the nicest things about the film — perhaps because it's directed by 67-year-old Rob Reiner — is that it doesn't treat its characters as one small slip from a nursing home.

"There are awkward moments in it," Keaton admits. "It's funny when Michael kisses me, because it's so awful, and awkward — but you know, that first kiss can always be awful and awkward. That doesn't go away with age! And hopefully that's something everyone can relate to. Humor is the great barrier-breaker."

Humor got her through her childhood, which was not unhappy but perhaps typically '50s — a slightly remote father, a fun but creatively unfulfilled mother, and the usual worries, kept in journals and recounted in her delightful 2011 memoir "Then Again." ("Dear Diary: I wish I had a boyfriend. Boys are never going to like me because I'm flat. Well, maybe one boy might, but I'm not sure.")

"My mother always encouraged me," Keaton says. (Perhaps the reason she later took her mother's maiden name as her stagename; her birthname is actually Hall.) "I couldn't have asked for a better enabler — and I mean that in the best possible way! She never said 'Here's a lesson' but her lesson to me was, go ahead. Fulfill your dreams."

'Annie Hall' made Keaton's career, and remains the stand-out of eight films with Woody Allen

When a teacher in her California high school predicted that "someday I'd be a great comedian," Keaton told her diary she was not particularly convinced ("Har de har.") But she was a hit in her senior-year musical, and was soon trying her luck in Manhattan, living in a theatrical boardinghouse and taking serious drama classes.

"That changed everything," she said. "(Acting teacher) Sanford Meisner changed everything. I thought I was going to be a singer, maybe do musical-comedies, but he introduced me to things I didn't even know I had in me. He introduced me to rage. He introduced me to living in the moment. And some of these principles apply to your life."

Because, she says, she wasn't just learning about acting. She was really learning about being honest.

"In a scene, you want to be there with your partner, respond to your partner," she explains. "It's not just, 'Am I getting my objective in this scene?' For it to work, you have to be with the other person, adjust your responses to that person. And for me, that resonates in my life. People matter, you know? It's kind of a way of being there."

Keaton was living in a $98.32-a-month walk-up in 1968 — and barely making rent — when she got a part in "Hair." (She still turned down the $50 bonus, offered if you stripped onstage). The next year she got a role in a new play by Woody Allen, "Play It Again, Sam"; it led to an awkward dinner ("I think I had a date," she wrote her mother afterward), and a relationship. And then, a longtime collaboration.

"I didn't have a sense of what a movie was when we started, even though I'd already been in 'The Godfather,'" she says. "I remember going to the sets for 'Sleeper' and thinking, This is moviemaking? This is more like summer camp! On 'The Godfather,' there were marks you had to hit, 'Don't move your head!' — that was awful for me, coming out of Sandy's classes where you're constantly responding to what's happening. But with Woody, everything was just very loose... We played like a couple of idiots and I couldn't have had a better time."
That soon changed, in a good way.

For Keaton, making 'Sleeper' with Allen was like going to summer camp

"The dividing line was `Annie Hall,'" she says. "He was writing differently by then; it wasn't just a string of jokes. He still wasn't very confident about the script, he was very self-deprecating about it as usual, I mean, but really. 'Get over it, Woody!' you know, 'This is great!' It had a lot of substance behind it, and hiring Gordon (Willis, the cinematographer) just stretched his visual palette enormously. It was unique, and it was easy. It was the easiest part I ever played."

It was a dividing line in another way — although she would follow it up for Allen with "Manhattan," and the glum "Interiors," their work together was quietly winding down (their relationship had already ended). They remained friends, though, and later reteamed for 1993's "Manhattan Murder Mystery" — seen by some as a way for Allen to recapture the past, and get away from the ugly details of his recent split with Mia Farrow.

Those stories cropped up again at this year's Golden Globes, when a beaming Keaton picked up Allen's honorary award; Farrow and two of her children immediately denounced the tribute and the winner, accusing him again of sexual abuse. Of the old scandal, Keaton has only stated, simply, "I believe my friend"; of the harsh personal criticism she faced for supporting him, she says now, with a weary stammer, "Yeah, well, you know — what are you going to do?"

What Keaton always did, even when working with Allen, was to look for other, interesting work. She returned for "The Godfather Part II" and was even more heartbreaking (partly, perhaps, because she no longer had to deal with "that horrible blonde wig" they'd given her in the first one). And she was startling in "Looking for Mr. Goodbar," a deliberately difficult, provocative film about casual sex (and violence) in a newly liberated generation.

Playing Louse in 'Reds,' Keaton says, was one of her biggest challenges

If "Annie Hall" was the easiest part she ever played, though, taking on radical journalist Louise Bryant in Warren Beatty's 1981 epic "Reds" would be one of the hardest.

"The thing is, I didn't really like her," Keaton says frankly. "She's one of those people who wants to be something better than she is, like Salieri — she's riddled with envy, and that's pretty unattractive. But it was a good part, one of the more complex roles I've gotten — there was this edge to her, and this conflict, torn between how much she loved John Reed and how much she wanted to be seen as better than he was. Which she wasn't! Yeah, I don't know, it was just very, very hard to play her."

Still, Keaton says, one thing she never does is bring any story's dark moods home.

"I get out of it, at the end of the day, but still you have to get into it, you know?" she says. "Me, I'm in awe of people like Meryl Streep, who can play every possible imaginable character and in ways I never could. With accents? And this transformational kind of acting? Wow. I mean, wow. That's really somebody who has a huge storage in her soul to empathize and identify with everything. I just go, wow... I'm a great fan. I'm a great audience. I love actors. I love them."

Of course, quite frankly, she literally has — in addition to Allen, Keaton has had relationships with Warren Beatty, and with Al Pacino. But she and her partners never seemed to be in sync when it came to commitment, or family. Finally, single at 50, Keaton looked into adoption. She now has two children, a daughter named Dexter and a son named Duke.

Keaton was in all all three 'Godfather' movies, but loathed the wig they made her wear in the first one

"My mother didn't get to fulfill her own ambitions, creatively, and you pay a price for that," Keaton says. "And so I put my career as No. 1 in my agenda for a long time and you pay a price for that. You pay a price for everything. But I got lucky, too."

Sometimes it seemed her movie luck was running out; at times, she wondered if she had trusted too much in being someone else's muse, and not enough in her own vision.
"Without a great man writing and directing for me," she writes in "Then Again," "I was a mediocre movie star at best."

She was too hard on herself. Even as acting — and men — were disappointing her, she was still finding fulfillment in other ways. She made a quirky documentary, "Heaven," and an oddball feature, "Unstrung Heroes." She edited books of photography, and mounted shows of her own decidedly unique pictures (one was a study of hotel lobbies).

'Something's Gotta Give' marked a new turn in Keaton's career

And, as a new decade began, her movie career rebounded, chiefly in romantic comedies — two "Father of the Bride" movies with Steve Martin, the genuinely fun "The First Wives Club" and, in 2003, the hit farce with Jack Nicholson, "Something's Gotta Give." (Her next projects include "Life Itself," with Morgan Freeman, and providing the voice of Ellen DeGeneres' mom in the "Finding Nemo" sequel, "Finding Dory.")

Next year will mark her 45th year in the movies. And yet Keaton remains not only unjaded but energized, amassing followers on Twitter and still totally in love with acting.

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"That never goes away," she says. "You slip into someone else's life and get to play it free of charge — oh, Michael Douglas loves me! But it's just in the movie, and you act it out, and then you go to another story. I just look forward to plunging into these people — that's it for me."

And best of all, she's still learning, she says.

"I warn directors now, I'm a sloppy actress," she says. "I like to try things, and I'm really bad at a lot of them. But I keep taking different shots at stuff, because you never know what's going to come out of a mistake. Sometimes your approach can be wrong, but it can be right for you. I think that's my life story, you know? Sometimes, wrong is right."